Chapter 5

Chemical Bonding and Molecular Structure

The atoms of many elements can combine to form molecules. The atoms in most molecules are
held together by strong attractive forces called chemical bonds. These bonds are formed via the
interaction of the valence electrons of the combining atoms. The chemical and physical properties
of the resulting molecules are often very different from those of their constituent elements.

In addition to the very strong forces within a molecule, there are weaker intermolecular forces
between molecules. These intermolecular forces, although weaker than the intramolecular
chemical bonds, are of considerable importance in understanding the physical properties of many
substances. We shall discuss intermolecular forces in greater detail when we look at the different
phases of matter later on. Processes that involve the breaking and forming of chemical bonds are
generally considered chemical processes, while those that only involve interactions between
molecules are generally considered physical processes.

In the formation of chemical bonds, many molecules contain atoms bonded according to the octet
rule, which states that an atom tends to bond with other atoms until it has eight electrons in its
outermost shell, thereby forming a stable electron configuration similar to that of the noble gas
elements. Exceptions to this rule are as follows: hydrogen, which can have only two valence
electrons (the configuration of He); lithium and beryllium, which bond to attain two and four
valence electrons, respectively; boron, which bonds to attain six; and elements beyond the second

Ionic   Bonds   and Ionic   Compounds

Covalent    Bonds

Lewis   Structures

Types   of  Covalent    Bonding

Geometry    and Polarity    of  Covalent    Molecules

Orbital Hybridization

Sigma   and Pi  Bonds